{ INFORMATICS.MCCME.RU
  Problem statement: http://informatics.mccme.ru/moodle/mod/statements/view3.php?chapterid=265
  Verdict: Accepted
}
uses SysUtils, Math;
 
var
	a,b,c,kk,mm,ans:int64;
 
begin
reset(input,'input.txt');
rewrite(output,'output.txt');
read(a,b,c);
if c<=a then ans:=b*2 else begin
	kk:=(2*c) div a;
	mm:=(2*c) mod a;
	if mm>0 then inc(kk);
	ans:=kk*b;
end;
write(ans);
end.